Melatonin induces mitochondrial apoptosis in osteoblasts by regulating the STIM1/cytosolic calcium elevation/ERK pathway

Idiopathic scoliosis is a common deformity of the spine that has an especially high incidence rate in adolescents. Some studies have demonstrated a close relationship between idiopathic scoliosis and melatonin deficiency. Our team's previous research showed that melatonin can inhibit the proliferation of osteoblasts, but the mechanism remains unclear. This study aimed to determine the mechanism by which melatonin inhibits the proliferation of osteoblasts. Cell viability experiment, DNA fragment detection and alkaline phosphatase (ALP) activity assays were performed to determine the effects of melatonin on the proliferation, apoptosis and differentiation of osteoblasts. We used immunofluorescence to detect the expression of STIM1 in melatonin-treated osteoblasts. STIM1 interference was achieved using a specific siRNA, and a TRPC inhibitor was used to block the influx of Ca2+. The mRNA expression was determined by RT-qPCR, and protein levels were measured by Western blot. In this study, we found that melatonin inhibited the proliferation, differentiation and apoptosis of osteoblasts in a concentration-dependent manner. Additional studies showed that melatonin elevated cytosolic calcium levels by upregulation of STIM1, leading to osteoblast apoptosis via the mitochondrial pathway. Finally, we demonstrated that the STIM1-mediated increase in cytosolic calcium levels induced apoptosis through the ERK pathway. Melatonin induces mitochondrial apoptosis in osteoblasts by regulating the STIM1/cytosolic calcium elevation/ERK pathway. These basic findings provide a basis for further clinical studies on melatonin as a drug therapeutic for idiopathic scoliosis.